Discharge tube for laser oscillator

ABSTRACT

At least one pair of electrodes (5a, 5b) are provided on the surface of a dielectric discharge tube (1), and radiating fins (2a, 2b) are attached to a part of the electrodes (5a, 5b). A ceramic clamp (3) and a stainless-steel backup plate (4) are engaged with recessed portions of the radiating fins (2a, 2b), to thereby fix the radiating fins (2a, 2b) in position. Accordingly, a rise in the temperature of the electrodes is reduced by radiating heat through the radiating fins, whereby a separation or deterioration of the electrodes (5a, 5b) is prevented.

TECHNICAL FIELD

The present invention relates to a discharge tube for a laser oscillatorused in a gas laser oscillator, and more particularly, to a dischargetube for a laser oscillator adapted to be driven by a high-frequency(including radio frequencies) ac power source.

BACKGROUND ART

In a gas laser oscillator, a dielectric discharge tube is generallyformed of ceramics or quartz, a pair of electrodes are arranged on theouter surface of the discharge tube, and a high-frequency ac power isapplied to these electrodes to excite gas in the discharge tube tothereby cause an electric discharge. Reflecting mirrors are providedseparately on opposite sides of the discharge tube to thus form a laseroscillator.

The electrodes may be formed by a metal deposition process or by bondinga metallic tape to the surface of the discharge tube.

When the ac power is applied to the discharge tube to cause an electricdischarge, however, the temperature inside the discharge tube rises, andas a result, the discharge tube temperature reaches 300° C. orthereabouts. Accordingly, a problem has arisen in that the electrodesare separated due to the difference in coefficient of thermal expansionbetween a dielectric constituting the discharge tube and a metalconstituting the electrodes. Moreover, as the temperature of theelectrode rises, the temperature of the ambient air rises, and thus acorona discharge occurs at the end portions of the electrodes, whichcauses a deterioration of the electrodes.

Therefore, to prevent a separation of the electrodes, a cushion isconventionally interposed between the electrodes and the discharge tube,and to prevent the corona discharge, a molded material, such assilicone, is applied to the end portions of the electrodes.

These processes require a reprocessing of the discharge tube, and themanufacture of the discharge tube requires substantial man-hours.

DISCLOSURE OF THE INVENTION

The present invention has been contrived in consideration of thesecircumstances, and an object thereof is to provide a discharge tube fora laser oscillator, in which the discharge tube is provided withradiating fins to prevent a rise in the temperature of electrodes.

To solve the above problem, according to the present invention, there isprovided a discharge tube for a laser oscillator, which comprises atleast one pair of electrodes formed on the surface of a dielectricdischarge tube, and radiating fins attached to the respective endportions of the electrodes.

Accordingly, a rise in temperature of the electrodes is prevented by aradiation of heat therein through the radiating fins provided on theelectrodes.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1(a) is a diagram showing a discharge tube for laser oscillatoraccording to one embodiment of the present invention; and

FIG. 1(b) is a side view corresponding to FIG. 1(a).

BEST MODE OF CARRYING OUT THE INVENTION

One embodiment of the present invention will now be described withreference to the drawings.

FIG. 1(a) is a diagram showing a discharge tube for a laser oscillatoraccording to one embodiment of the present invention, and FIG. 1(b) is aside view corresponding to FIG. 1(a). As shown in the Figures, a ceramicor quartz pipe is used as the discharge tube 1, and a pair of electrodes5a and 5b are arranged spirally on the surface of the discharge tube 1.These electrodes 5a and 5b may formed by a metal deposition process orby bonding a metallic tape thereto.

Aluminum radiating fins 2a and 2b are arranged separately on oppositesides of the discharge tube 1, and in close contact with the electrodes5a and 5b, respectively. This is accomplished by cutting out a quartercircle from an end portion of each of the radiating fins 2a and 2b.Further, the central portion of each radiating fin is recessed to befixed to the discharge tube 1. A ceramic clamp 3 and a stainless-steelbackup plate 4 are engaged with the respective recessed portions of theradiating fins 2a and 2b, to thereby fix the radiating fins 2a and 2b inposition. The clamp 3 is formed of ceramic material, and therefore, iscoupled to members 6a and 6b by screws 7a and 7b, and the members 6a and6b are coupled to the backup plate 4 by screws 8a and 8b, respectively.

The backup plate 4 is flexible, and thus holds the radiating fans 2a and2b on the discharge tube 1 by the spring function thereof. The clamp 3is formed of ceramic material because a ceramic material has a smallcoefficient of expansion when subjected to a rise in temperature. Thebackup plate 4 is formed of a stainless steel, because the tenacity ofstainless steel is not lowered by a high temperature.

Accordingly, even if the temperature of the discharge tube 1 isincreased by an electric discharge, the resulting heat is radiated intothe air via the radiating fins 2a and 2b, and therefore, a rise in thetemperature of the electrodes 5a and 5b, which are heated to aparticularly high temperature, is prevented. The use of these radiatingfins enables the temperature to be lowered by a margin of about 100° to150° C., when used in a CO₂ gas laser with an output of 1 kW orthereabout. If the output of the laser is higher, the temperature of theelectrodes can be further lowered by air-cooling the radiating fins 2aand 2b by a fan.

Therefore, a separation of the electrodes 5a and 5b from the dischargetube 1 can be prevented, and further, a deterioration of the electrodes5a and 5b due to a corona discharge is also prevented.

It is to be understood that this effect can be also produced with theuse of electrodes formed by a metal deposition process or by a metallictape.

According to the present invention, as described above, the temperaturerise attributable to an electric discharge is reduced by fitting theradiating fins to the end portions of the electrodes, and thus aseparation or deterioration of the electrodes can be prevented.

We claim:
 1. A discharge tube for a laser oscillator, comprising:atleast one pair of electrodes formed on a surface of a dielectricdischarge tube; and radiating fins attached to respective end portionsof said electrodes, said radiating fins each having a recessed portionin the center, said recessed portion being fixed to said discharge tubeby a clamp and a tenacious backup plate.
 2. Discharge tube structure fora laser oscillator comprising:a dielectric discharge tube; a firstelectrode having a first end portion; a second electrode having a secondend portion, said first and second end potions being disposed in spacedrelationship relative to one another on the outer surface of saiddischarge tube; a first heat radiating fin assembly mounted on said tubeand including a segment disposed in close heat conducting contact withsaid first end portion; and a second heat radiating fin assembly mountedon said tube and including a segment disposed in close heat conductingcontact with said second end portion.
 3. A discharge tube structure asset forth in claim 2, wherein said end portions are disposed on oppositesides of said discharge tube.
 4. A discharge tube structure as set forthin claim 3, wherein is included a single clamp device for holding saidsegments of the first and second assemblies on said tube in said closeheat conducting contact with said electrode end portions.
 5. A dischargetube structure as set forth in claim 2, wherein each of said electrodesis formed by a metal deposition process.
 6. A discharge tube structureas set forth in claim 2, wherein each of said electrodes is formed of ametallic tape.
 7. A discharge tube structure as set forth in claim 2,wherein said radiating fins are formed of aluminum.
 8. A discharge tubestructure as set forth in claim 4, wherein each of said segmentscomprises a recessed portion in the center of the respective assembly,said device including a clamp and a tenacious backup plate for holdingthe segments against the corresponding end portion.
 9. A discharge tubestructure as set forth in claim 2, wherein is included a fan forair-cooling said radiating fins.